Steerable catheter with adjustable bend location

ABSTRACT

Steerable catheter having an adjustable bend location comprising a flexible elongate tubular member having proximal and distal extremities. A plurality of circumferentially spaced-apart flexible elements are disposed in the distal extremity for causing bending of the distal extremity of the flexible elongate member. A bend positioner is disposed at the distal extremity of the flexible elongate member for selecting the location in the distal extremity of the flexible elongate tubular member where bending is to occur to thereby adjust the length of the flexible elongate member which extends beyond the bend.

This is a continuation of application Ser. No. 07/983,962, filed Dec. 1,1992, now abandoned.

This invention relates to a steerable catheter with an adjustable bendlocation and method.

In certain procedures, as for example ablation procedures for use with asteerable catheter in the human heart, it has been found that it isdifficult to provide a bend in the appropriate location in the distalextremity of the steerable catheter while maintaining the rigidity ofthe distal extremity. This has found to be particularly true in patientshaving large hearts. There is therefore a need for a new and improvedsteerable catheter which overcomes these difficulties.

In general, it is an object of the present invention to provide asteerable catheter with an adjustable bend location and method.

Another object of the invention is to provide a catheter and method ofthe above character which can be utilized with different types ofbending mechanisms for the distal extremity of the catheter.

Another object of the invention is to provide a catheter and method ofthe above character in which the adjustment of the bend location can bereadily accomplished.

Additional objects and features of the invention will appear from thefollowing description in which the preferred embodiments are set forthin detail in conjunction with the accompanying drawings.

FIG. 1 is a side elevational view of a steerable catheter incorporatingthe present invention.

FIG. 2 is a side elevational view partially in cross-section showing oneembodiment of a steerable catheter incorporating the present inventionutilizing a shape-memory element.

FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 2.

FIGS. 4A, 4B and 4C show four examples of how an adjustable bendlocation in the steerable catheter makes possible bends in differentlocations in the distal extremity of the catheter.

FIG. 5 is a diagrammatic illustration showing the manner in which thesteerable catheter of the present invention can be utilized in a humanheart to provide a different bend location to make it possible to reachdifficult-to-reach portions of the wall forming a chamber in the heart.

FIG. 6 is a partial cross-sectional view of another embodiment of asteerable catheter incorporating the present invention utilizingremovable stiffening elements having weakened portions at differentlongitudinal positions of the stiffening elements.

FIG. 7 is a cross-sectional view taken along the line 7--7 of FIG. 6.

FIGS. 8A, 8B and 8C show stiffening elements having weakened regions indifferent longitudinal portions of the stiffening element.

FIG. 9 is a partial cross-sectional view of the distal extremity ofanother embodiment of a steerable catheter incorporating the presentinvention utilizing telescoping stiffening elements.

FIG. 10 is a cross-sectional view taken along the line 10--10 of FIG. 9.

In general, the steerable catheter of the present invention consists ofa flexible elongate tubular member having proximal and distalextremities. A plurality of circumferentially spaced-apart flexibleelements are disposed in the distal extremity for causing bending of thedistal extremity of the flexible elongate member. Movable means isdisposed in the distal extremity of the flexible elongate member forselecting the location where bending in the distal extremity will takeplace.

More in particular, the steerable catheter 11 incorporating the presentinvention consists of a flexible elongate member 12 formed of a suitablematerial such as plastic which is provided with proximal and distalextremities 13 and 14. An ablation electrode 16 is carried by the distalextremity 14. A hand-held control mechanism 17 is mounted on theproximal extremity 13. The hand-held control mechanism 17 can be ofvarious types. For example it can be of the type which can be utilizedfor actuating pull wires (not shown) extending longitudinally of theflexible elongate tubular member 12 which are well known to thoseskilled in the art and which can be utilized for bending the distalextremity of the flexible elongate tubular member 12. Alternatively, itcan be provided with means for controlling flexible elongate elementshaving a negative coefficient of expansion disposed in the distalextremity 14 of the flexible elongate tubular member 12 as described inco-pending application Ser. No. 07/793,858, filed Nov. 18, 1991. Meansnot shown in FIG. 1 is provided for adjusting the bend location in thedistal extremity of the flexible elongate tubular member 12 which willhereinafter be described in conjunction with specific embodiments of thepresent invention.

In FIGS. 2 and 3 there is disclosed a steerable catheter 21 whichconsists of a flexible elongate tubular member 22 which is provided withproximal and distal extremities 23 and 24. A metal ablation electrode 26is secured to the distal extremity 24. A hand-held control mechanism 27is mounted on the proximal extremity 23 of the flexible elongate tubularmember 22. The flexible elongate tubular member 22 is formed of asuitable material such as plastic and is provided with a plurality ofcircumferentially spaced-apart lumens 31-36, and a central lumen 37, allof which extend the length of the flexible elongate tubular member 22. Aplurality of flexible elongate elements, as for example three of suchelements 41, 42 and 43, are disposed 120° apart and are provided in thelumens 31, 33 and 35. These flexible elongate elements 41, 42 and 43 aredisposed in the distal extremity 24 of the flexible elongate tubularmember 22 and are formed of a material which has a negative coefficientof expansion. The distal extremities of these flexible elongate members41, 42 and 43 are connected to a common ground return 44 provided in thelumen 34. The three flexible elongate elements 41, 42 and 43 are alsoconnected to conductors (not shown) which extend to the proximalextremity 23 of the flexible elongate member and with the ground return44 connected into a cable 46 extending from the control mechanism 17 andare connected to a joystick control console 47 of the type described inco-pending application Ser. No. 07/793,858, filed Nov. 18, 1991, andwhich includes a joystick 48. The ablation electrode 26 is connected bya conductor 51 provided in the lumen 32 and extending into the controlmechanism 17 and is connected to a suitable ablation power supply (notshown) conventionally used with such catheters.

Bend location adjustment means 56 is provided in the distal extremity 24of the flexible elongate tubular member 22 and consists of ashape-memory element 57 formed of a suitable material such as Nitinolwhich has been provided with a memory which makes it assume a straightcondition when it is heated such as by the application of electricalenergy thereto. The shape-memory element 57 is provided with proximaland distal extremities 58 and 59. The proximal extremity 58 is connectedby a joint 61 to a conductor 62 which extends into the control mechanismand is connected as hereinafter described. The distal extremity 59 isconnected to a ground return conductor 44 by wire 63. The shape-memoryelement 57 can have a suitable diameter, as for example 5-20 mils. Thebend adjustment means 56 also includes selective conductive bypass means66 which is movable longitudinally along the length of the shape-memoryelement 57 to selectively inhibit current flow in a portion of theshape-memory element to permit bending of the shape-memory element 57 inthat portion of the shape-memory element.

The conductive bypass means 66 as shown in FIGS. 2 and 3 consists of anelongate cylindrical sleeve 67 formed of a suitable conducting material,as for example a silver mesh or braid, through which the shape-memoryelement 57 extends. Means is provided for adjusting the sleeve 67longitudinally over the shape-memory element 57 and consists of aflexible tubular member 68 formed of a suitable insulating material suchas plastic which is slidably mounted in the central lumen 37. Thetubular member 68 is provided with a bore 69 therein extending thelength thereof and in which the shape-memory element 57 is disposed. Ascan be seen particularly in FIG. 2, the sleeve 67 has one end secured tothe distal extremity of the flexible tubular member 68. The other end ofthe sleeve 67 is supported by another tubular member 71 of the samematerial and of the same diameter as the flexible tubular member 68 andis provided with a bore 72 through which the shape-memory element 57extends. The sleeve 67 can be affixed to the tubular members 68 and 71by suitable means such as an adhesive.

In order to ensure good conductivity between the silver braid or meshsleeve 67, the shape-memory element should be cleaned with nitric andhydrochloric acids to remove any oxidation which may be present on theshape-memory element 57. This ensures that there is good electricalcontact between the sleeve 67 and the shape-memory element so thatminimal or no current flows in the portion of the shape-memory element57 which is covered by the sleeve.

Means is provided for controlling the movement of the flexible tubularmember 68 and the sleeve 67 carried thereby from the control mechanism27 and consists of a control member 76 which is secured to the proximalextremity of the tubular member 68. The control member 73 extendsdiametrically of the tubular member 68 through a longitudinallyextending slot 77 provided in the sidewall of a cylindrical housing 78.The cylindrical housing 78 can be formed of a suitable material such asplastic or metal, and is sized in such a manner so that it is adapted tobe held by the human hand. For example, it can have a diameter ofapproximately 1" and a length of 5-6". It is provided with a cylindricalrecess 79 therein permitting the control member 76 with the attachedflexible tubular member 68 to move therein relative to the conductor 62which is mounted in an end cap 81 secured to the proximal extremity ofthe housing 78. The conductor 62 is connected to a cable 82 whichextends out of the housing 78 and is connected to a variable currentpower supply 83 which is provided with a control knob 84 to adjust theamount of current which is supplied to the sleeve 67. The variablecurrent power supply 83 is also provided with another cable 86 which isconnected to the ground return conductor 44.

Operation and use of the steerable catheter 21 may now be brieflydescribed as follows. Let it be assumed that it is desired to form abend in the distal extremities 24 of the flexible elongate tubularmember 22 in the position where the sleeve 67 has been located bymovement of the control member 76. Current is supplied under the controlof the control knob 84 from the variable current power supply 83 to theshape-memory element 57. The shape-memory element 57, when it issupplied with electrical energy, attempts to return to its memorizedcondition which, as pointed out before, is a straight condition. At thesame time, it becomes stiffer. The conductive sleeve 67 however permitsthe portion of the shape-memory element 57 covered by the sleeve toremain flexible. This occurs because the sleeve 67, which is in closeintimate contact with the shape-memory element 57, serves as a currentbypass or bridge and causes the current to flow through the highlyconductive silver mesh sleeve 67 to thereby bridge that portion of theshape-memory element 57 covered thereby so that it remains relativelyflexible. Thus, the portion of the shape-memory element 57 underlying orwithin the sleeve 67 does not heat up and remains flexible and does notattempt to assume the straight condition of the remainder of theshape-memory element 57. By adjusting the longitudinal position of thesleeve with respect to the shape-memory element 57, it is possible toadjust the location at which the shape-memory element 57 will beflexible to permit bending at different locations so that shorter orlonger straight or stiff portions can be provided at the distalextremity of the catheter 11 beyond the bend. Examples of such differentlocations of bends is shown by the bends 91, 92 and 93 in FIGS. 4A, 4Band 4C, respectively which show progressively longer stiff portionsextending distally beyond the bends.

FIG. 5 shows by providing different bend locations for the steerablecatheter 11, it is possible to reach difficult-to-reach positions in thehuman heart. Two different bends represented by the bends 94 and 96 inthe catheter 11 are shown in which the bend 96 in contradistinction tothe bend 94 makes it possible to reach a difficult-to-reach area of thewall 96 forming the chamber 97 of the human heart 98.

Another embodiment of a steerable catheter incorporating the presentinvention is shown in the catheter 101 in FIGS. 6 and 7 which consistsof a flexible elongate tubular member 102 formed of a suitable materialsuch as plastic which is provided with a distal extremity 103 having ametal electrode 104 provided thereon. The flexible elongate member 102is provided with a plurality of circumferentially spaced-apart lumens106-111 and a central lumen 112. At least three pull wires 116, 117 and118 are provided in the lumens 106, 108 and 109, which are connectedinto the distal extremity and which extend to the proximal end of thecatheter 101 and are controlled by a conventional control mechanism (notshown) for causing bending of the distal extremity of the tubularelongate member 102. A conductor 119 is provided in the lumen 110 and isconnected to the electrode 104. An elongate stiffening element 121 isslidably mounted in the central lumen 112. This stiffening element 121is provided with a weakened longitudinal portion 121a of the stiffeningelement 121. This weakened portion 121a can be of a suitable length, asfor example 1-5 cm. It can be seen that by utilizing such a stiffeningelement with such a weakened portion that the bending of the distalextremity 103 of the flexible elongate tubular member 102 will occur inthe region of the weakened portion 121a.

In the event that it is desirable to provide a bend which has a longerstiffer portion extending beyond the bend, the stiffener element 121 canbe interchanged with other stiffener elements, as for example stiffenerelements 126, 127 and 128, as shown in FIGS. 8A, 8B and 8C, havingweakened longitudinal portions 126a, 127a and 128a, respectively, atdifferent longitudinal positions of the stiffener elements 126, 127 and128. It can be seen that by selecting an appropriate stiffener elementthat the bend in the distal extremity of the flexible elongate member102 can be made to occur in the desired location to provide differenthinge points and also to provide different lengths of the stiffenerelement extending beyond the weakened region or hinge point.

Another embodiment of a steerable catheter incorporating the presentinvention is shown in the steerable catheter 131 depicted in FIGS. 9 and10. As shown therein, the catheter 131 consists of a flexible elongatemember 132 formed of a suitable material such as plastic which isprovided with a distal extremity 133 to which there is secured a tipelectrode 134. The flexible elongate member 132 is provided with aplurality of circumferentially spaced-apart lumens 137-142 and a centrallumen 143. At least three flexible elongate elements 146, 147 and 148are disposed in the lumens 136, 138 and 139 and are formed of a materialhaving a negative coefficient of expansion. Their distal extremities areconnected to a common ground return conductor 149 provided in the lumen141. A conductor 151 is provided in the lumen 137 and is connected tothe electrode 134. The flexible elongate elements 146, 147 and 148 areconnected to a joystick-type of control hereinbefore described inconnection with the embodiment as shown in FIG. 2, and for that reasonis not shown in FIGS. 9 and 10.

The means for adjusting the bend location for the bending of the distalextremity 133 of the flexible elongate tubular member 132 is in the formof a telescoping assembly 151 formed of a suitable material such asstainless steel mounted in the central lumen of the distal extremity 133of the catheter 131. The telescoping assembly 151 is movable betweencollapsed and extended positions and consists of an outer cylindricalmember 152 which is secured within the distal extremity 133 by suitablemeans such as an adhesive. The outer cylindrical member is provided witha cylindrical bore 153 and a swaged end 154 providing an opening 155 incommunication with the bore 153. An intermediate cylindrical member 156is slidably mounted within the outer cylindrical member 152 and isprovided with a flanged end 157 which is adapted to engage the swagedend 154 of the outer cylindrical member 152. The intermediatecylindrical member 156 is provided with a bore 158 and has a swaged end159 forming a hole 161 extending therethrough. An inner cylindricalmember 164 is provided which has a flange 166 which is adapted to travelin the bore 158. The inner cylindrical member 164 travels through thehole 161 and forms the distal extremity of an elongate flexiblepush-pull element 171 which extends to the proximal extremity (notshown) of the flexible elongate member 132. The flexible elongateelement 171 can be formed of a suitable material such as stainless steeland can have a diameter of 0.012-0.025". It is provided a portion 171aof reduced diameter in close proximity to the inner cylindrical member164 as shown in FIG. 9. By way of example, it can have a reduceddiameter ranging from 0.006" to 0.015". The diameter of the flexibleelongate element 171 should be of a diameter which is slightly greaterthan the size of the hole 161 for a purpose hereinafter described.

In utilizing the steerable catheter 131 shown in FIG. 9, the hinge pointor bend location for the distal extremity 133 of the flexible elongateelement 132 can be readily adjusted. For example, for the shortestpossible stiff or straight length extending beyond the bend, thetelescoping assembly 151 is in a collapsed position in which thepush-pull element 171 has been pushed towards the distal extremity sothat the distal extremity of the flexible elongate member 171 is inengagement with the proximal extremity of the intermediate cylindricalmember 156 and the intermediate cylindrical member is disposed entirelywithin the outer cylindrical member 132. To increase the length of thisstiff portion extending beyond the bend, it is merely necessary towithdraw proximally the flexible elongate element 171 which will firstpull the inner cylindrical member 164 proximally to increase the lengthof the stiff portion extending beyond the bend provided by the region171a. To provide a still longer stiff portion extending beyond the bend,it is merely necessary to pull proximally the flexible elongate member171 to cause the intermediate cylindrical member 156 to be pulled out ofthe outer cylindrical member 152 to thereby increase the length of thetelescoping assembly 151 and to also increase the length of the stiffportion extending beyond the bend or hinge point 171a. Thus, it can beseen that by use of the telescoping assembly 151 and by pushing orpulling on the flexible elongate element 171 it is possible to adjustthe length of the telescoping assembly and to thereby adjust the lengthof the stiff portion extending beyond the bend.

From the foregoing it can be seen that there have been provided a numberof different embodiments of an invention in which it is possible toadjust the bend location in the distal extremity of a steerable catheterwhich makes it possible for the steerable catheter to be utilized tomove its tip into many different locations, and particularly intolocations which are difficult to reach with conventional steerablecatheters. This is particularly advantageous in ablation procedureswhere it is desired to precisely locate the ablation electrode forperforming an ablation procedure.

What is claimed is:
 1. In a steerable catheter having a continuouslyadjustable bend location along the distal axial length thereof, aflexible elongate tubular member having proximal and distal extremities,a control mechanism secured to the proximal extremity, a plurality ofcircumferentially spaced-apart flexible elements disposed in the distalextremity for causing bending of the distal extremity of the flexibleelongate member and movable means controlled by the control mechanismdisposed at the distal extremity of the flexible elongate member forselecting the location in the distal extremity where bending is to occurto thereby adjust the length of the flexible elongate member whichextends beyond the bend, said movable means being in the form of ashape-memory element having a memory which makes it assume a straightposition upon the application of an electrical current thereto andbypass means adjustable longitudinally of the shape-memory element forcausing the current applied to the shape-memory element to bypass aportion of the length of the shape-memory element so that it remainsflexible at that portion to provide a hinge point for the bend.
 2. In asteerable catheter having an adjustable bend location, a flexibleelongate tubular member having proximal and distal extremities, aplurality of circumferentially spaced-apart flexible elements disposedin the distal extremity for causing bending of the distal extremity ofthe flexible elongate member and movable means adjustably disposed atthe distal extremity of the flexible elongate member for selecting whilethe steerable catheter is use the location in the distal extremity wherebending is to occur to thereby adjust the length of the flexibleelongate member which extends beyond the bend, said movable means beingin the form of a shape-memory element having a memory which makes itassume a straight position upon the application of an electrical currentthereto and bypass means adjustable longitudinally of the shape-memoryelement for causing the current applied to the shape-memory element tobypass a portion of the length of the shape-memory element so that itremains flexible at that portion to provide a hinge point for the bend,said bypass means consisting of a conductive sleeve movablelongitudinally of the shape-memory element.
 3. A catheter as in claim 2wherein said sleeve is in the form of conductive mesh of a highlyconductive material.
 4. A catheter as in claim 2 together with meanscoupled to said sleeve for moving said sleeve longitudinally of saidshape-memory element, said means coupled to the sleeve extending to theproximal extremity of the flexible elongate member.
 5. A catheter as inclaim 4 together with a control mechanism mounted on the proximalextremity of the flexible elongate member, said control mechanismincluding a control member movable longitudinally thereof and connectedto the member coupled to the sleeve.
 6. A catheter as in claim 4 whereinsaid means coupled to said sleeve is in the form of a tubular memberhaving a bore therein and wherein said shape-memory element extendsthrough said bore.
 7. In a steerable catheter having an adjustable bendlocation, a flexible elongate tubular member having proximal and distalextremities, a plurality of circumferentially spaced-apart flexibleelements disposed in the distal extremity for causing bending of thedistal extremity of the flexible elongate member and removable meansdisposed at the distal extremity of the flexible elongate member forselecting while the steerable catheter is in use in the body of apatient the location in the distal extremity where bending is to occurto thereby adjust the length of the flexible elongate member whichextends beyond the bend, said removable means being a selected one of aplurality of stiffening elements, each stiffening element having aweakened region providing a hinge point in a different longitudinalposition of the stiffening element than the longitudinal positions ofthe other of said stiffening elements.
 8. A catheter as in claim 7wherein said stiffening element is comprised of an elongate flexiblemember of a predetermined cross-section and wherein said weakened regionis formed by producing a region of reduced cross-section.
 9. In asteerable catheter having an adjustable bend location, a flexibleelongate tubular member having proximal and distal extremities, acontrol mechanism secured to the proximal extremity, a plurality ofcircumferentially spaced-apart flexible elements disposed in the distalextremity of the flexible elongate tubular member for causing bending ofthe distal extremity of the flexible elongate member and movable meanscontrolled by the control mechanism disposed at the distal extremity ofthe flexible elongate member for selecting while the steerable catheteris in use the location in the distal extremity where bending is to occurto thereby adjust the length of the flexible elongate member whichextends beyond the bend, said movable means being in the form of atelescoping assembly movable between collapsed and extended positionsand comprising at least first and second telescoping memberstelescopically mounted with respect to each other disposed in the distalextremity of the flexible elongate member, flexible elongate meansextending to the proximal extremity of the flexible elongate member andcoupled to said second telescoping member of said telescoping assemblyfor moving said telescoping assembly between said collapsed and extendedpositions, said flexible elongate means coupled to said telescopingassembly including a weakened longitudinal portion which forms a hingepoint.
 10. A steerable catheter having an adjustable bend location, aflexible elongate tubular member having proximal and distal extremities,a plurality of stiffening elements, one of said stiffening elementsbeing disposed in said elongate tubular member and having a weakenedregion providing a hinge point different from the hinge points of theother of said stiffening elements, said other of the stiffening elementshaving weakened regions providing hinge points in different longitudinalpositions of the stiffening element whereby when different stiffeningelements are inserted into the flexible elongate tubular member, thedistal extremity of the flexible elongate tubular member has a differenthinge point.